CN117802603A - Recycled regenerated cotton pulp lyocell fiber and preparation method thereof - Google Patents
Recycled regenerated cotton pulp lyocell fiber and preparation method thereof Download PDFInfo
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- 229920000433 Lyocell Polymers 0.000 title claims abstract description 51
- 238000002360 preparation method Methods 0.000 title claims abstract description 24
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- 239000001913 cellulose Substances 0.000 claims abstract description 76
- 239000002002 slurry Substances 0.000 claims abstract description 71
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 64
- 238000009987 spinning Methods 0.000 claims abstract description 58
- 230000008961 swelling Effects 0.000 claims abstract description 42
- 238000013329 compounding Methods 0.000 claims abstract description 27
- 229920001131 Pulp (paper) Polymers 0.000 claims abstract description 25
- 239000003513 alkali Substances 0.000 claims abstract description 22
- 229910001385 heavy metal Inorganic materials 0.000 claims abstract description 19
- 238000001914 filtration Methods 0.000 claims abstract description 16
- 230000003213 activating effect Effects 0.000 claims abstract description 15
- 229920000875 Dissolving pulp Polymers 0.000 claims abstract description 14
- 239000003381 stabilizer Substances 0.000 claims abstract description 14
- 239000003963 antioxidant agent Substances 0.000 claims abstract description 13
- 230000003078 antioxidant effect Effects 0.000 claims abstract description 12
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 59
- 238000000034 method Methods 0.000 claims description 37
- 238000001994 activation Methods 0.000 claims description 30
- 230000004913 activation Effects 0.000 claims description 29
- LFTLOKWAGJYHHR-UHFFFAOYSA-N N-methylmorpholine N-oxide Chemical compound CN1(=O)CCOCC1 LFTLOKWAGJYHHR-UHFFFAOYSA-N 0.000 claims description 24
- 238000007664 blowing Methods 0.000 claims description 21
- 239000007864 aqueous solution Substances 0.000 claims description 17
- 238000002156 mixing Methods 0.000 claims description 17
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- 238000004519 manufacturing process Methods 0.000 claims description 12
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- 229910021641 deionized water Inorganic materials 0.000 claims description 11
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- 238000001035 drying Methods 0.000 claims description 9
- 150000001875 compounds Chemical class 0.000 claims description 8
- 238000007599 discharging Methods 0.000 claims description 7
- ZTHYODDOHIVTJV-UHFFFAOYSA-N Propyl gallate Chemical group CCCOC(=O)C1=CC(O)=C(O)C(O)=C1 ZTHYODDOHIVTJV-UHFFFAOYSA-N 0.000 claims description 6
- 238000004061 bleaching Methods 0.000 claims description 5
- 238000001891 gel spinning Methods 0.000 claims description 4
- AVXURJPOCDRRFD-UHFFFAOYSA-N hydroxylamine group Chemical group NO AVXURJPOCDRRFD-UHFFFAOYSA-N 0.000 claims description 3
- 235000010388 propyl gallate Nutrition 0.000 claims description 3
- 239000000835 fiber Substances 0.000 abstract description 47
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- RBLWMQWAHONKNC-UHFFFAOYSA-N hydroxyazanium Chemical compound O[NH3+] RBLWMQWAHONKNC-UHFFFAOYSA-N 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention discloses a recycled regenerated cotton pulp lyocell fiber and a preparation method thereof. The preparation method comprises the following steps: selecting and compounding recycled cotton pulp, activating, swelling aqueous cellulose, dissolving swelling slurry, buffering and standing the dissolved slurry, and spinning. The preparation method comprises the steps of selecting recycled and regenerated cotton pulp which accords with heavy metal ions, alkali and alkaline earth ions, ash content, polymerization degree and cellulose content, compounding the recycled and regenerated cotton pulp with different polymerization degrees or dissolving wood pulp, adjusting the polymerization degree within a proper range, activating, adding a stabilizer and an antioxidant, vacuumizing and dissolving, buffering and standing the dissolving pulp before spinning, refining and filtering, and the like, so as to obtain the lyocell fiber which accords with the quality requirement. The advantages are that: is suitable for industrialized large-scale application; recycling the recycled cotton pulp in a high proportion; the fiber quality is high.
Description
Technical Field
The invention relates to the field of regenerated cellulose fibers, in particular to a regenerated cotton pulp lyocell fiber and a preparation method thereof.
Background
Regenerated cellulose fibers are mainly of two types: viscose fiber and environmental friendly solvent Lajersey fiber (English name Lyocell). As early as one hundred years, a production process of viscose fiber is developed by taking cellulose as a raw material, but a large amount of toxic and harmful waste water and waste gas are generated in the preparation process of viscose fiber, so that the development of viscose fiber is restricted. The production process of the lyocell fiber developed by taking N-methylmorpholine oxide NMMO as a solvent system has no industrial pollution, low energy consumption, simple process, excellent fiber performance and biodegradability after the product is discarded.
The production of waste cotton textiles reaches 1200 ten thousand tons per year, and if the waste cotton textiles can be made into regenerated cotton pulp, cheng Laisai mol of fibers can be prepared by using the regenerated cotton pulp, so that the resource pressure can be relieved, and the energy and the carbon can be saved. However, the preparation process of the lyocell fiber is a pure physical process, and the requirements on raw pulp are very strict. The cellulose fibers currently produced using the lyocell process are also limited to dedicated dissolving pulp sources (e.g., sappi pulp or cosmo pulp). The problems of poor spinnability, poor spinning fiber performance and the like when lyocell fiber spinning is carried out are caused by the large difference of the raw material characteristics, the using degree and the impurity content of the waste cotton textiles. The Oryland extract company mixes a small amount of recycled cotton with Lyocell virgin wood pulp at the end of 2019 to realize the recycling of the recycled cotton LYOCELL fiber Refibra for the first time TM But the proportion of the waste cotton pulp used by the spinning can only reach 10 percent.
Therefore, a method for solving the problems of high-quality lyocell fiber spinning by mixing recycled cotton pulp in a high proportion and being applicable to industrialized large-scale preparation is needed.
Disclosure of Invention
In order to overcome the technical problems, the invention aims to provide the lyocell fiber for industrially producing and recycling the regenerated cotton pulp and the preparation method thereof.
The invention is characterized in that: the recycled regenerated cotton pulp has a large amount of impurities and large difference in polymerization degree distribution, the content of heavy metal ions, alkali and alkaline earth ions and the polymerization degree distribution in the recycled regenerated cotton pulp are strictly controlled, and the recycled regenerated cotton pulp is compounded with dissolving wood pulp to ensure that the polymerization degree of the formed pulp is in a better range, so that the fiber spinnability is improved; the degradation of pulp and the uniformity stability of slurry are improved by adding antioxidant and stabilizer in the activation and swelling processes, buffering and standing, and the like, and the quality and yield of the finished product of the industrially produced fiber are improved, so that a feasible way for recycling the regenerated cotton pulp by high-value utilization suitable for industrial production is found.
In order to achieve the above object, the present invention provides a method for preparing lyocell fiber from recycled and regenerated cotton pulp, comprising the steps of (in the present invention, "wt%" means mass%):
1. selecting and compounding recycled cotton pulp: selecting recycled and regenerated cotton pulp with the polymerization degree of 400-1000, the alpha cellulose content of more than or equal to 92%, the ash content of less than or equal to 0.1%, the heavy metal ion content of less than or equal to 20ppm and the alkali and alkaline earth ion content of less than or equal to 400 ppm; the recycled and regenerated cotton pulp with different polymerization degrees is selected for compounding, or the recycled and regenerated cotton pulp with different polymerization degrees is compounded with the dissolved wood pulp, the mixing proportion of the recycled and regenerated cotton pulp is not less than 70%, and the polymerization degree of the compounded pulp is 550-800;
2. activating: putting the compounded pulp into an activation tank according to a proportion, adding deionized water, adjusting the pH value to 4-6, adding cellulose complex enzyme for activation, adding alkali liquor, adjusting the pH value to 10-13, and stopping activation to obtain aqueous cellulose;
3. swelling: removing water from the activated aqueous cellulose, keeping the aqueous cellulose at 30-60 wt%, adding an aqueous solution containing 50-88 wt% of N-methylmorpholine oxide, and then adding 1-5 wt% of antioxidant and 1-5 wt% of stabilizer to obtain swelling slurry;
4. dissolving: the swelling slurry enters a double-screw extruder, and is heated, vacuumized, dehydrated, dissolved and defoamed to obtain dissolved slurry;
5. buffer and standing: dissolving the slurry in a buffer tank at 70-90 deg.c for 30-60 min;
6. spinning: filtering, buffering and standing the dissolved slurry, conveying the dissolved slurry to a metering pump by using a booster pump, and spinning by adopting a dry-wet method to obtain the recycled regenerated cotton pulp lyocell fiber.
Further, in the preparation method of the lyocell fiber of the recycled and regenerated cotton pulp provided by the invention, the recycled and regenerated cotton pulp in the step 1 is preferably 500-800 in polymerization degree, the content of heavy metal ions is less than or equal to 10ppm, and the content of alkali and alkaline earth ions is less than or equal to 200ppm; the polymerization degree of the dissolving wood pulp is preferably 400-600.
Further, in the preparation method of the recycled and regenerated cotton pulp lyocell fiber provided by the invention, the compounding scheme in the step 1 is as follows: the regenerated cotton pulp adopted by the compounding does not exceed 3 polymerization degrees; the polymerization degree of the regenerated cotton pulp with the highest mass ratio is not higher than 700, and the usage amount is not lower than 40%; the amount of dissolved wood pulp is not more than 30%.
Further, in the preparation method of the recycled and regenerated cotton pulp lyocell fiber provided by the invention, the dosage of the cellulose complex enzyme in the step 2 is preferably 0.01-0.1 wt%, the activation time is 30-90 minutes, and the polymerization degree of the aqueous cellulose is regulated to be 500-700.
Further, in the preparation method of the recycled and regenerated cotton pulp lyocell fiber provided by the invention, the mass content of cellulose in the swelling slurry in the step 3 is 8-12 wt% and the pH value is 8-12; the mass ratio of the aqueous cellulose to the 50-88 wt% of the aqueous solution of the N-methylmorpholine oxide in the swelling slurry is 1: (2-12), and the discharging temperature is 50-80 ℃; the antioxidant in the swelling slurry is n-propyl gallate, the stabilizer is hydroxylamine, the mass ratio of the aqueous cellulose in the swelling slurry to the antioxidant of 1 to 5 weight percent is 1 (0.1 to 0.125), and the mass ratio of the aqueous cellulose in the swelling slurry to the stabilizer of 1 to 5 weight percent is 1 (0.02 to 0.08).
Further, in the preparation method of the recycled regenerated cotton pulp lyocell fiber provided by the invention, the cellulose content of the dissolved pulp in the step 4 is 11-15 wt%, the feeding temperature of the dissolved pulp is 50-80 ℃, and the discharging temperature is 90-120 ℃.
Further, in the preparation method of the recycled and regenerated cotton pulp lyocell fiber provided by the invention, a filter element is arranged in a filter used for filtering in the step 6, and the accuracy is 10-80 mu m.
Further, in the preparation method of the recycled and regenerated cotton pulp lyocell fiber provided by the invention, the dry and wet spinning process conditions in the step 6 are that the spinning speed is 35-100 m/min, the spinning air gap is 5-50 mm, the spinning blowing temperature is 10-25 ℃, the spinning blowing flow is 100-500L/H, the blowing relative humidity is 50-80%, the coagulation bath concentration is 10-30%, the coagulation bath temperature is 5-30 ℃, and the draft ratio is 1: (5-10).
Further, the preparation method of the recycled regenerated cotton pulp lyocell fiber provided by the invention further comprises a post-treatment step 7, wherein the post-treatment step 7 comprises water washing, bleaching, oiling and drying.
In addition, the invention also provides the lyocell fiber of the recycled and regenerated cotton pulp prepared by the method, which is prepared by adopting the recycled and regenerated cotton pulp, wherein the proportion of the recycled and regenerated cotton pulp is not lower than 70%, and the recycled and regenerated cotton pulp selects pulp with the polymerization degree of 400-1000, the alpha cellulose content of not less than 92%, the ash content of not more than 0.1%, the heavy metal ion content of not more than 20ppm and the alkali and alkaline earth ion content of not more than 400 ppm.
Compared with the prior art, the invention provides the recycled and regenerated cotton pulp lyocell fiber and the preparation method thereof, and has the following beneficial effects: (1) The mixing proportion of the recycled cotton pulp is greatly improved, can reach up to 100 percent, and is not lower than 70 percent at the minimum, thereby providing a high-value waste cotton textile utilization way suitable for industrial production. (2) The content of heavy metal ions in the recycled cotton pulp is controlled, so that the safe production of spinning is ensured. The feasibility of mass production of the recycled regenerated cotton pulp is ensured by selecting the recycled regenerated cotton pulp meeting the requirements of polymerization degree, alpha cellulose content, ash content, alkali and alkaline earth ions and the like, and compounding the recycled regenerated cotton pulp or compounding the recycled regenerated cotton pulp with the dissolved wood pulp. (3) The molecular chain of the cotton pulp is opened through an activation process, the polymerization degree is adjusted, the solvent NMMO is promoted to dissolve cotton cellulose, the requirement of the lyocell fiber process on the raw material pulp is further met, the spinnability of the dissolving pulp is increased, and the safety of the fiber processing process is ensured. (4) In the fiber preparation process, dissolving pulp is buffered and kept stand, spinning pulp is homogenized and defoamed in advance, so that the orientation degree is increased, the characteristics of compact molecular chain structure and high crystallinity of cotton pulp cellulose are overcome, and the fibrillation tendency of fibers is reduced. (5) The stabilizer and the antioxidant are added, so that the stability of the slurry is ensured, the degradation of the slurry is reduced, the recovery cost of NMMO solvent is reduced, the production safety is improved, and the method is suitable for manufacturing the lyocell fiber for large-scale industrial continuous production. (6) The prepared lyocell fiber has full hand feeling, strong water absorption, high strength in wet state and good dimensional stability, and can be used for producing high-end fabrics.
Detailed Description
The lyocell fiber production system has strict requirements on the content of heavy metal ions, mainly because NMMO, which is a solvent used in the lyocell fiber process, is used as an oxidant, and a series of side reactions and even possible explosions occur in the presence of the metal ions.
If the content of alkali and alkaline earth ions in raw pulp is high, inorganic salt particles can block spinneret holes during spinning forming, which is unfavorable for spinning forming and can influence the quality of spinning lyocell fibers.
The pulp as raw material must be suitable for the expected fiber manufacturing and processing production line, so the polymerization degree of the pulp as raw material, the heavy metal content in the pulp, the alkali and alkaline earth ion content, ash content and the like all meet certain requirements, and the lyocell fiber meeting the quality requirements can be successfully spun by combining with the optimization of the subsequent process.
The invention provides a preparation method of recycled and regenerated cotton pulp lyocell fibers, which comprises the following steps: the method comprises the steps of selecting and compounding recycled regenerated cotton pulp, activating the compounded recycled regenerated cotton pulp, swelling the aqueous cellulose fiber, dissolving the swelled pulp, buffering and standing the dissolved pulp, and spinning. The method comprises the steps of selecting proper recycled cotton pulp, regulating the polymerization degree of the pulp through compounding, then treating the pulp through processes of activation, stabilizer addition, buffering and standing, fine filtration and the like to meet the requirements of the lyocell fiber process on the raw material pulp, and preparing the recycled cotton pulp lyocell meeting the quality requirements through optimizing the subsequent process in a large scale.
The preparation method provided by the invention comprises the following steps:
1. and (3) selecting and compounding recycled cotton pulp. Selecting recycled and regenerated cotton pulp with the polymerization Degree (DP) of 400-1000, the alpha cellulose content of more than or equal to 92%, the ash content of less than or equal to 0.1%, the heavy metal ion content of less than or equal to 20ppm and the alkali and alkaline earth ion content of less than or equal to 400 ppm; the recycled and regenerated cotton pulp with different polymerization degrees is selected for compounding, or the recycled and regenerated cotton pulp with different polymerization degrees is compounded with the dissolved wood pulp, DP adjustment is carried out on the feed pulp, and the polymerization degree of the feed pulp after adjustment is 550-800.
(1) The choice of recovering regenerated cotton pulp and dissolving wood pulp. The recycled pulp preferably has a heavy metal ion content of less than or equal to 20ppm, alkali and alkaline earth ion content of less than or equal to 400ppm, and the polymerization degree of the dissolving wood pulp is preferably 400-600. More preferably, the polymerization degree of the recycled and regenerated cotton pulp is 500-800, the content of heavy metal ions is less than or equal to 10ppm, and the content of alkali and alkaline earth ions is less than or equal to 200ppm; the dissolving wood pulp is preferably sappi wood pulp. The mixing proportion of the recycled and regenerated cotton pulp is not less than 70%.
(2) The compounding of recycled cotton pulp. The regenerated cotton pulp adopted by the compounding does not exceed 3 polymerization degrees; the polymerization degree of the regenerated cotton pulp with the highest mass ratio is not higher than 700, and the usage amount is not lower than 40%; the amount of dissolved wood pulp is not more than 30%. The compounding method has a plurality of methods: the method can be used for compounding 3 kinds of recycled cotton pulp with different polymerization degrees, the mixing proportion of the recycled cotton is up to 100%, 2 kinds of recycled cotton pulp with 1 kind of polymerized dissolved wood pulp can be used for compounding, 2 kinds of polymerized dissolved wood pulp with 1 kind of polymerized recycled cotton pulp can be used for compounding, 1 kind of recycled cotton pulp with 1 kind of polymerized wood pulp can be used for compounding, and 2 kinds of recycled cotton pulp can be used for compounding.
2. Activating. Proportionally adding the pulp with the DP in an activation tank, adding deionized water, adjusting the pH value to 4-6, adding cellulose complex enzyme for activation, adding alkali liquor, adjusting the pH value to 10-13, stopping activation, and obtaining the aqueous cellulose, wherein the polymerization degree of the aqueous cellulose is controlled to be 500-700.
(1) With respect to deionized water. Conductivity of deionized water<5us/cm 2 。
(2) With respect to cellulases. The cellulase is liquid cellulase, and can be obtained by BIOPRACTThe product of AL70 (product number IPL5B 0660). The degree of polymerization DP of the aqueous cellulose is adjusted to 500-700. The cellulase activity under the acidic condition is best, and the molecular chain of the cotton cellulose crystallization area is opened, so that the solvent NMMO is beneficial to dissolve cellulose.
3. Swelling. Removing the water in the activated aqueous cellulose to make the mass percentage content of the aqueous cellulose be 30-60 wt%, then adding an aqueous solution containing 50-88 wt% of N-methyl morpholine oxide, and then adding 1-5 wt% of antioxidant and 1-5 wt% of stabilizer to obtain swelling slurry.
(1) With respect to the swollen slurry. The cellulose content in the swelling slurry is 8-12 wt% and the pH value is 8-12. The mass ratio of the aqueous cellulose to the 50-88 wt% of the aqueous solution of the N-methylmorpholine oxide in the swelling slurry is 1: (2-12); the discharging temperature is 50-80 ℃.
(2) With respect to antioxidants and stabilizers. The antioxidant in the swelling slurry is preferably n-propyl gallate, and the stabilizer is preferably hydroxylamine; the mass ratio of the water-containing cellulose in the swelling slurry to the antioxidant is 1 (0.1-0.125), and the mass ratio of the water-containing cellulose in the swelling slurry to the stabilizer is 1 (0.02-0.08).
4. Dissolving. The obtained swelling slurry enters a double-screw extruder, and then is heated, vacuumized, dehydrated and dissolved to obtain dissolved slurry. The cellulose content of the dissolved slurry is 11-15 wt%, the feeding temperature of the dissolved slurry is 50-80 ℃, the discharging temperature is 90-120 ℃, and the vacuum degree is 1.0-15.0 kPa.
5. And (5) buffering and standing. And (5) buffering and storing the dissolved slurry, homogenizing and defoaming to obtain spinning slurry. The slurry is kept still for caching for 30-60 minutes, and the standing temperature is 70-90 ℃. The buffer, standing and preserving are preferably carried out by applying nitrogen to pressurize, and the pressure value is preferably 0.2 kPa-1.0 kPa, thereby being beneficial to homogenizing and defoaming the dissolved pulp, increasing the orientation degree of the pulp, overcoming the characteristics of compact molecular chain structure and high crystallinity of cellulose of the cotton pulp and reducing the fibrillation tendency of the fibers.
6. Spinning. Filtering the dissolved slurry, and filtering the dissolved slurry by using a filter, wherein a filter element with the accuracy of 10-80 mu m is arranged in the preferential filter; and then the recycled regenerated cotton pulp lyocell fiber is obtained by conveying the recycled regenerated cotton pulp to a metering pump by using a booster pump and adopting a dry-wet spinning method.
Preferably, the dry-wet spinning process conditions are that the spinning speed is 35-100 m/min, the spinning air gap is 5-50 mm, the spinning blowing temperature is 10-25 ℃, the spinning blowing flow is 100-500L/H, the blowing relative humidity is 50-80%, the coagulating bath concentration is 10-30%, the coagulating bath temperature is 5-30 ℃, and the draft ratio is 1: (5-10).
7. Post-treatment: washing with water, bleaching, oiling and drying.
The fiber is washed by deionized water during water washing, and the water washing temperature is 20-60 ℃. The solvent N-methylmorpholine-N-oxide adsorbed on the fiber can be recovered and purified for reuse.
The bleaching process adopts hydrogen peroxide for bleaching, the circulation concentration of hydrogen peroxide is 1.0% -2.0%, the circulation pH value of hydrogen peroxide is 8-10, and the circulation temperature is 60-80 ℃.
The circulating concentration of the oiling agent is 0.5-5%, the circulating pH value of the oiling agent is 6-9, and the circulating temperature of the oiling agent is 50-70 ℃.
The drying temperature is 80-120 ℃ during drying.
Example 1
Selecting a recycling regenerated cotton pulp and a composite blending scheme: 3 recovered regenerated cotton pulp with polymerization degree of 400-1000, alpha cellulose content of more than or equal to 92%, ash content of less than or equal to 0.1%, heavy metal ion content of less than or equal to 10ppm and alkali and alkaline earth ion content of less than or equal to 200ppm is selected for compound blending. The polymerization degrees of the 3 recovered regenerated cotton pulp were 600, 700 and 800, respectively. The DP600 recovered regenerated cotton pulp is taken as main pulp for compound blending, and the dosage is not less than 40 percent. The specific blending scheme is as follows: DP600 was 70%, DP700 was 20% and DP800 was 10%.
Activating: adding the compounded pulp into an activation tank, adding deionized water, adjusting the pH value to 4, adding cellulose complex enzyme for activating for 30 minutes, adding sodium hydroxide for stopping activation, and adjusting the pH value to 10.5.
Swelling: after the activated slurry is dehydrated in vacuum, controlling the water content of the water-containing cellulose to be 46%, adding 70% of N-methylmorpholine-N-oxide aqueous solution, adding 2% of PG and 1.5% of hydroxylammonium, wherein the mass ratio of the water-containing cellulose to the N-methylmorpholine-N-oxide aqueous solution is 1:4, the mass ratio of the water-containing cellulose to the PG is 1:0.125, the mass ratio of the water-containing cellulose to the hydroxylammonium is 1:0.05, swelling the slurry, and the discharging temperature is 60 ℃.
Dissolving: the index of the pre-dissolving pulp tested was 11% cellulose and pH 9.5. And (3) feeding the swelled pre-dissolved pulp into a double-screw dissolver, and controlling the vacuum degree to be 4.0kPa and the screw rotating speed to be 12r/min. The test dissolution slurry indexes are: cellulose 13% and the degree of polymerization DP of the dissolving pulp was adjusted to 500.
Buffer and standing: the dissolved slurry was placed in a buffer tank, pressurized with nitrogen at 0.2kPa, buffered for 30 minutes at a storage temperature of 70 ℃.
Spinning: filtering the dissolved slurry, wherein a filter is used for filtering, and a filter element is arranged in the filter element, so that the accuracy is 40 mu m; then the mixture is conveyed to a metering pump by a booster pump and sprayed out by a spinneret plate, and is formed by dry and wet spinning, wherein the spinning speed is 40m/min, the spinning air gap is 15mm, the spinning blowing temperature is 15 ℃, the spinning blowing flow is 250L/H, the blowing relative humidity is 50%, the concentration of a coagulating bath is 18%, the temperature of the coagulating bath is 10 ℃, and the draft ratio is 1:5.
post-treatment: washing the fiber with water at 60 ℃; oiling the fiber after water washing, wherein the circulating concentration of the oiling agent is 1.0%, the circulating pH value of the oiling agent is 6.5, and the circulating temperature of the oiling agent is 50 ℃; and drying the oiled fiber at 105 ℃. The obtained finished fiber index is: the fineness is 1.67dtex, the dry breaking strength is 4.0cN/dtex, the dry breaking elongation is 15%, the wet modulus is 0.9cN/dtex/5%, the fiber defect, namely the doubling content is 20mg/100g, and the fiber ISO whiteness is 80%.
Example 2
Selecting a recycling regenerated cotton pulp and a composite blending scheme: 3 recovered regenerated cotton pulp with polymerization degree of 400-1000, alpha cellulose content of more than or equal to 92%, ash content of less than or equal to 0.1%, heavy metal ion content of less than or equal to 10ppm and alkali and alkaline earth ion content of less than or equal to 200ppm is selected for compound blending. The polymerization degrees of the 3 recovered regenerated cotton pulp were 550, 600 and 700, respectively. The DP550 recovered regenerated cotton pulp is taken as main pulp for compound blending, and the dosage is not less than 40 percent. The specific blending scheme is as follows: 40% of DP550, 30% of DP600 and 30% of DP 700.
Activating: adding the compounded slurry into an activation tank, adding deionized water, adjusting the pH value to 5, adding cellulose compound enzyme for activation for 50 minutes, adding sodium hydroxide for stopping activation, adjusting the pH value to 11, and stopping activation.
Swelling: after the activated pulp porridge is dehydrated in vacuum, controlling the water content of the water-containing cellulose to be 50%, adding 71% of N-methylmorpholine-N-oxide aqueous solution, adding 2% of PG and 1.5% of hydroxylammonium, wherein the mass ratio of the water-containing cellulose to the N-methylmorpholine-N-oxide aqueous solution is 1:6, the mass ratio of the water-containing cellulose to the PG is 1:0.125, the mass ratio of the water-containing cellulose to the hydroxylammonium is 1:0.05, swelling pulp, and the outlet temperature is 65 ℃.
Dissolving: the pre-dissolving pulp was tested for an index of 11% cellulose content and a pH of 9.5. The pre-dissolved slurry after swelling enters a double-screw dissolver, the vacuum degree is controlled to be 5.0kPa, and the screw rotating speed is 12r/min. A dissolving pulp was obtained, the index of which was 13% of cellulose content and the degree of polymerization of the dissolving pulp was 580.
Buffer and standing: the dissolved slurry was placed in a buffer tank, pressurized with nitrogen gas at 0.2kPa, buffered for 30 minutes at a storage temperature of 70 ℃.
Spinning: filtering the obtained dissolved slurry by adopting a filter, wherein a filter element is arranged in the filter, and the accuracy is 50 mu m; then the mixture is conveyed to a metering pump by a booster pump and sprayed out by a spinneret plate, and is formed by dry and wet spinning, wherein the spinning speed is 50m/min, the spinning air gap is 12mm, the spinning blowing temperature is 15 ℃, the spinning blowing flow is 250L/H, the blowing relative humidity is 50%, the concentration of a coagulating bath is 18%, the temperature of the coagulating bath is 10 ℃, and the draft ratio is 1:5.
post-treatment: washing the spun fibers with water at a temperature of 60 ℃; oiling the fiber after water washing, wherein the circulating concentration of the oiling agent is 1.0%, the circulating pH value of the oiling agent is 6.5, and the circulating temperature of the oiling agent is 50 ℃; and drying the oiled fiber at 105 ℃. The obtained finished fiber index is as follows: the fineness is 1.58dtex, the dry breaking strength is 4.1cN/dtex, the dry breaking elongation is 15.2%, the wet modulus is 1.0N/dtex/5%, the fiber defect, namely the doubling content, is 15mg/100g, and the fiber ISO whiteness is 82%.
Example 3
Selecting a recycling regenerated cotton pulp and a composite blending scheme: 2 recovered regenerated cotton pulp with polymerization degree of 500-800, alpha cellulose content of more than or equal to 92%, ash content of less than or equal to 0.1%, heavy metal ion content of less than or equal to 20ppm and alkali and alkaline earth ion content of less than or equal to 400ppm are selected to be compounded and blended with sappi dissolving wood pulp. The polymerization degree of the 2 recovered regenerated cotton pulp was 600 and 700 respectively. The DP600 recovered regenerated cotton pulp is taken as main pulp for compound blending, and the dosage is not less than 40 percent. The polymerization degree of sappi dissolved wood pulp is 600, and the use amount is not more than 30% and is between 400 and 600. The specific blending scheme is as follows: 45% DP600, 25% DP700 and 30% sappi dissolving pulp DP 600.
Activating: putting the compounded pulp into an activation tank, adding deionized water, adjusting the pH value to 6, adding cellulose compound enzyme for activating for 60 minutes, adding sodium hydroxide for stopping activation, adjusting the pH value to 11, and stopping activation.
Swelling: the activated pulp porridge is dehydrated in vacuum, the water content percentage of the water-containing cellulose is controlled to be 40%, 75% of N-methylmorpholine-N-oxide aqueous solution is added, 2% of PG and 1.5% of hydroxylammonium are added, wherein the mass ratio of the water-containing cellulose to the N-methylmorpholine-N-oxide aqueous solution is 1:5, the mass ratio of the water-containing cellulose to the PG is 1:0.125, the mass ratio of the water-containing cellulose to the hydroxylammonium is 1:0.05, the pulp is swelled, and the outlet temperature is 65 ℃. The indexes of the detection pre-dissolved pulp are as follows: cellulose content 11.5% and pH 9.5.
Dissolving: the obtained swelling slurry (namely pre-dissolving slurry) enters a double-screw dissolver, the vacuum degree is controlled to be 6.0kPa, and the screw rotating speed is 12r/min. Detecting the index of the dissolving slurry: the cellulose content was 13.5% and the degree of polymerization DP of the dissolving pulp was 610.
Buffer and standing: the dissolved slurry was placed in a buffer tank, pressurized with nitrogen gas at 1.0kPa, buffered for 30 minutes at a storage temperature of 70 ℃.
Spinning: filtering the dissolved slurry, wherein a filter with a built-in filter element is used, and the precision is 30 mu m; then the mixture is conveyed to a metering pump by a booster pump and sprayed out by a spinneret plate, dry and wet spinning is adopted for forming, the spinning speed is 60m/min, the spinning air gap is 10mm, the spinning blowing temperature is 10 ℃, the spinning blowing flow is 300L/H, the blowing relative humidity is 50%, the concentration of a coagulating bath is 20%, the temperature of the coagulating bath is 10 ℃, and the draft ratio is 1:8.
post-treatment: washing the spun fibers with water at a water washing temperature of 60 ℃; after water washing, the fiber is oiled, the circulating concentration of the oiling agent is 1.0%, the circulating pH value of the oiling agent is 6.5, and the circulating temperature of the oiling agent is 50 ℃; and drying the oiled fiber at 105 ℃.
The obtained finished fiber index is: the fineness is 1.33dtex, the dry breaking strength is 4.5cN/dtex, the dry breaking elongation is 15%, the wet modulus is 1.1cN/dtex/5%, the fiber defect, namely the doubling content is 8mg/100g, and the fiber ISO whiteness is 80%.
Example 4
As comparative example 1, the feasibility and fiber quality of spinning recycled regenerated cotton pulp lyocell fibers of examples 1 to 3 in the present invention were verified.
Pulp selection: only recycled cotton pulp is selected, and dissolving wood pulp is not selected. Other indexes of the selected recycled cotton pulp meet the requirements, the polymerization degree is also in the range of 400-1000, but the selected recycled cotton pulp is the endpoint value of the lower limit.
Activating: and (3) putting the recovered regenerated cotton pulp with the polymerization degree DP of 400 into an activation tank, adding deionized water, adjusting the pH value to 6, adding cellulose complex enzyme for activating for 30 minutes, adding sodium hydroxide for stopping activation, adjusting the pH value to 10.5, and stopping activation.
Swelling: after the activated pulp porridge is dehydrated in vacuum, controlling the water content of the water-containing cellulose to be 45%, adding 71% of N-methylmorpholine-N-oxide aqueous solution, adding 2% of PG and 1.5% of hydroxylammonium, wherein the mass ratio of the water-containing cellulose to the N-methylmorpholine-N-oxide aqueous solution is 1:4, the mass ratio of the water-containing cellulose to the PG is 1:0.125, the mass ratio of the water-containing cellulose to the hydroxylammonium is 1:0.05, swelling pulp, and detecting indexes of pre-dissolved pulp at an outlet temperature of 60 ℃ to be: 11% of cellulose and 9.5% of pH value.
Dissolving: after swelling, the mixture enters a double-screw dissolver, the vacuum degree is controlled to be 5.0kPa, and the rotating speed of the screw is controlled to be 12r/min. Detecting the index of the dissolving slurry: 13% cellulose and a dissolution slurry polymerization degree DP of 380.
Buffer and standing: the dissolved slurry was placed in a buffer tank, pressurized with nitrogen gas at 0.8kPa, buffered for 30 minutes at a storage temperature of 70 ℃.
Spinning: filtering the dissolved slurry, wherein a filter is used for filtering, and a filter element is arranged in the filter, so that the accuracy is 40 mu m; then the mixture is conveyed to a metering pump by a booster pump and sprayed out by a spinneret plate, and is formed by dry-wet spinning, the spinning speed is 35m/min, the spinning air gap is 20mm, the spinning blowing temperature is 15 ℃, the spinning blowing flow is 250L/H, the blowing relative humidity is 50%, the concentration of a coagulating bath is 18%, the temperature of the coagulating bath is 10 ℃, and the draft ratio is 1:5.
post-treatment: washing the fiber with water at 60 ℃; oiling the fiber after water washing, wherein the circulating concentration of the oiling agent is 1.0%, the circulating pH value of the oiling agent is 6.5, and the circulating temperature of the oiling agent is 50 ℃; and drying the oiled fiber at 105 ℃.
The obtained finished fiber: the fineness is 3.33dtex, the dry breaking strength is 3.0cN/dtex, the dry breaking elongation is 17%, the wet modulus is 0.50cN/dtex/5%, the fiber defect, namely the doubling content is 500mg/100g, and the fiber ISO whiteness is 80%.
Conclusion: the polymerization degree DP of the recycled and regenerated cotton pulp is low, so that the spinnability is poor during spinning, the spinning forming is difficult, the phenomena of yarn breakage and yarn floating during spinning are serious, the fiber defects are high, the yarn doubling rate is up to 500mg/100g, and the method cannot be applied to the weaving processing of back-end spinning.
Example 5
As comparative example 2, the feasibility and the fiber quality of the recycled regenerated cotton pulp lyocell fibers of examples 1 to 3 in the present invention were verified.
Pulp selection: only recycled cotton pulp is selected, and dissolving wood pulp is not selected. Other indexes of the selected recycled cotton pulp meet the requirements, and the polymerization degree is only not in the range of 400-1000.
Activating: putting the recovered regenerated cotton pulp with the polymerization degree DP of 1100 into an activation tank, adding deionized water, adjusting the pH value to 6, adding cellulose complex enzyme for activating for 80 minutes, adding sodium hydroxide for terminating activation, adjusting the pH value to 11, and terminating activation.
Swelling: vacuum dewatering the activated pulp porridge, controlling the water content of the water-containing cellulose to be 45%, adding 75% of N-methylmorpholine-N-oxide aqueous solution, adding 2% of PG and 1.5% of hydroxylammonium, wherein the water content of the water-containing cellulose and the N-methylmorpholine-N-oxide aqueous solution is 1:6, the water content of the water-containing cellulose and the N-methylmorpholine-N-oxide aqueous solution is 1:0.125, the water content of the water-containing cellulose and the hydroxylammonium is 1:0.05, swelling pulp, and the outlet temperature is 60 ℃, so that the obtained pre-dissolved pulp is indicated by the following steps: the cellulose content was 11% and the pH was 9.5.
Dissolving: the pre-dissolved liquid obtained after swelling is also called swelling slurry and enters a double-screw dissolver, the vacuum degree is controlled to be 6.0kPa, and the screw rotating speed is 12r/min. Obtaining a dissolving slurry, wherein the indexes of the testing solution slurry are as follows: cellulose content 12.5% and degree of polymerization DP of the dissolving pulp of 960.
Buffer and standing: the dissolved slurry was placed in a buffer tank, pressurized with nitrogen gas at 1.0kPa, buffered for 60 minutes at 80 ℃.
Spinning: filtering the dissolved slurry, wherein a filter is used for filtering, and a filter element is arranged in the filter, so that the accuracy is 10-80 mu m; other parameters were substantially the same as in example 2.
Conclusion: the selected recycled and regenerated cotton pulp has too high polymerization degree DP, and the viscosity is too high due to the fact that the dissolved wood pulp with low polymerization degree is not selected to be added for compounding. Because the viscosity is too high, dissolution cannot be fully completed, impurities in the dissolved slurry are too high, the dissolved slurry blocks the filter, the pressure of the filter is ultrahigh, the process danger is increased, the dissolved slurry still cannot be spun and molded through the filter, and the broken ends are too many, so that the large-scale production cannot be realized.
Example 6
The lyocell fiber index of the recovered regenerated cotton pulp obtained according to the preparation method in examples 1 to 3 and the spinning test results according to examples 4 to 5 (as comparative example 1 and comparative example 2, respectively) are collated in table 1. The slurry polymerization degree indicated in table 1 is the slurry polymerization degree obtained after activation, swelling, dissolution and buffer standing.
Table 1 examples 1 to 5 spinning test controls
It can be seen that: (1) The polymerization degree of the dissolved pulp is controlled to be 500-700 by preferably recovering the regenerated cotton pulp, compounding and adding the dissolved pulp, so that the compounded pulp can be ensured to be spun smoothly. (2) The content of heavy metal ions in the recycled and regenerated cotton pulp is preferably less than or equal to 20ppm, the content of alkali and alkaline earth ions is preferably less than or equal to 400ppm, the content of heavy metal ions in the recycled and regenerated cotton pulp can be controlled to be less than or equal to 10ppm after the dissolved wood pulp is added, the content of alkali and alkaline earth ions can be controlled to be less than or equal to 200ppm, the DP degradation of the polymerization degree of the dissolved pulp is less, the safety of fiber processing is ensured, the operation of the process steps is practical, and the adaptability to the raw material pulp is high. (3) The spun fiber has high strength and wet modulus, the strength can reach 4.5cN/dtex, and the wet modulus is more than or equal to 1.0cN/dtex/5%.
Claims (10)
1. The preparation method of the recycled and regenerated cotton pulp lyocell fiber is characterized by comprising the following steps:
(1) Selecting and compounding recycled cotton pulp: selecting recycled and regenerated cotton pulp with the polymerization degree of 400-1000, the alpha cellulose content of more than or equal to 92%, the ash content of less than or equal to 0.1%, the heavy metal ion content of less than or equal to 20ppm and the alkali and alkaline earth ion content of less than or equal to 400 ppm; the method comprises the steps of selecting recycled regenerated cotton pulp with different polymerization degrees for compounding, or compounding the recycled regenerated cotton pulp with different polymerization degrees with dissolved wood pulp, wherein the mixing proportion of the regenerated cotton pulp is not less than 70%; the polymerization degree of the compound pulp is 550-800;
(2) Activating: putting the compounded pulp into an activation tank according to a proportion, adding deionized water, adjusting the pH value to 4-6, adding cellulose complex enzyme for activation, adding alkali liquor, adjusting the pH value to 10-13, and stopping activation to obtain aqueous cellulose;
(3) Swelling: removing water from the activated aqueous cellulose, keeping the aqueous cellulose at 30-60 wt%, adding an aqueous solution containing 50-88 wt% of N-methylmorpholine oxide, and then adding 1-5 wt% of antioxidant and 1-5 wt% of stabilizer to obtain swelling slurry;
(4) Dissolving: the swelling slurry enters a double-screw extruder, and is heated, vacuumized, dehydrated, dissolved and defoamed to obtain dissolved slurry;
(5) Buffer and standing: dissolving the slurry in a buffer tank at 70-90 deg.c for 30-60 min;
(6) Spinning: filtering, buffering and standing the dissolved slurry, conveying the dissolved slurry to a metering pump by using a booster pump, and spinning by adopting a dry-wet method to obtain the recycled regenerated cotton pulp lyocell fiber.
2. The method for producing lyocell fiber of recycled and regenerated pulp as claimed in claim 1, wherein said recycled and regenerated pulp in said step (1) has a polymerization degree of 500 to 800, a heavy metal ion content of 10ppm or less, and alkali and alkaline earth ion contents of 200ppm or less; the polymerization degree of the dissolved wood pulp is 400-600.
3. The method for preparing the recycled and regenerated cotton pulp lyocell fiber according to claim 1, wherein the compounding scheme in the step (1) is as follows: the polymerization degree of the regenerated cotton pulp adopted by the compounding is not more than 3; the polymerization degree of the regenerated cotton pulp with the highest mass ratio is not higher than 700, and the usage amount is not lower than 40%; the amount of dissolved wood pulp used is not more than 30%.
4. The method for preparing lyocell fiber from recycled and regenerated cotton pulp according to claim 1, wherein the amount of the cellulose complex enzyme in the step (2) is 0.01 to 0.1wt%, the activation time is 30 to 90 minutes, and the polymerization degree of the aqueous cellulose is adjusted to 500 to 700.
5. The method for producing a recycled regenerated cotton pulp lyocell fiber according to claim 1, wherein the mass content of cellulose in the swollen slurry in the step (3) is 8 to 12% by weight, and the pH is 8 to 12; the mass ratio of the aqueous cellulose to the 50-88wt% aqueous solution of N-methylmorpholine oxide in the swelling slurry is 1: (2-12), and the discharging temperature is 50-80 ℃; the antioxidant in the swelling slurry is n-propyl gallate, the stabilizer is hydroxylamine, the mass ratio of the aqueous cellulose to 1-5 wt% of the antioxidant in the swelling slurry is 1 (0.1-0.125), and the mass ratio of the aqueous cellulose to 1-5 wt% of the stabilizer in the swelling slurry is 1 (0.02-0.08).
6. The method for preparing lyocell fiber of recycled and regenerated cotton pulp according to claim 1, wherein the cellulose content of the dissolving pulp in the step (4) is 11-15 wt%, the feeding temperature of the dissolving pulp is 50-80 ℃, and the discharging temperature is 90-120 ℃.
7. The method for preparing lyocell fiber of recycled and regenerated cotton pulp according to claim 1, wherein said filtering in said step (6) is carried out by installing a filter element in a filter with a precision of 10-80 μm.
8. The method for preparing the recycled and regenerated cotton pulp lyocell fiber according to claim 1, wherein the dry-wet spinning process condition in the step (6) is that a spinning speed is 35-100 m/min, a spinning air gap is 5-50 mm, a spinning blowing temperature is 10-25 ℃, a spinning blowing flow is 100-500L/H, a blowing relative humidity is 50% -80%, a coagulating bath concentration is 10% -30%, a coagulating bath temperature is 5-30 ℃, and a draft ratio is 1: (5-10).
9. The method for producing a recycled regenerated cotton pulp lyocell fiber according to claim 1, further comprising a post-treatment step (7) comprising washing with water, bleaching, oiling, and drying.
10. The recycled regenerated cotton pulp lyocell fiber prepared by the method of any one of claims 1 to 9, characterized in that the recycled regenerated cotton pulp is prepared, the proportion of the recycled regenerated cotton pulp is not less than 70%, the recycled regenerated cotton pulp is selected from pulp with a polymerization degree of 400-1000, an alpha cellulose content of not less than 92%, ash content of not more than 0.1%, heavy metal ion content of not more than 20ppm and alkali and alkaline earth ion content of not more than 400 ppm.
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